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Wed, 7 Apr 2021 20:57:41 -0700 (PDT) From: Roman Gushchin To: Dennis Zhou CC: Tejun Heo , Christoph Lameter , Andrew Morton , Vlastimil Babka , , , Roman Gushchin Subject: [PATCH v3 4/6] percpu: generalize pcpu_balance_populated() Date: Wed, 7 Apr 2021 20:57:34 -0700 Message-ID: <20210408035736.883861-5-guro@fb.com> X-Mailer: git-send-email 2.30.2 In-Reply-To: <20210408035736.883861-1-guro@fb.com> References: <20210408035736.883861-1-guro@fb.com> MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable X-FB-Internal: Safe Content-Type: text/plain X-Proofpoint-GUID: GFHEjN2cySM2Ia08pC_lfTknEp74SUIE X-Proofpoint-ORIG-GUID: GFHEjN2cySM2Ia08pC_lfTknEp74SUIE X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10434:6.0.391,18.0.761 definitions=2021-04-08_01:2021-04-07,2021-04-08 signatures=0 X-Proofpoint-Spam-Details: rule=fb_default_notspam policy=fb_default score=0 impostorscore=0 bulkscore=0 clxscore=1015 adultscore=0 malwarescore=0 priorityscore=1501 mlxscore=0 spamscore=0 phishscore=0 mlxlogscore=999 suspectscore=0 lowpriorityscore=0 classifier=spam adjust=0 reason=mlx scancount=1 engine=8.12.0-2104060000 definitions=main-2104080023 X-FB-Internal: deliver X-Rspamd-Queue-Id: A3083E000104 X-Stat-Signature: c8edxeox893xymx8cgjskchoqwh8j5j4 X-Rspamd-Server: rspam02 Received-SPF: none (fb.com>: No applicable sender policy available) receiver=imf05; identity=mailfrom; envelope-from=""; helo=mx0a-00082601.pphosted.com; client-ip=67.231.145.42 X-HE-DKIM-Result: pass/pass X-HE-Tag: 1617854269-826198 X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: To prepare for the depopulation of percpu chunks, split out the populating part of the pcpu_balance_populated() into the new pcpu_grow_populated() (with an intention to add pcpu_shrink_populated() in the next commit). The goal of pcpu_balance_populated() is to determine whether there is a shortage or an excessive amount of empty percpu pages and call into the corresponding function. pcpu_grow_populated() takes a desired number of pages as an argument (nr_to_pop). If it creates a new chunk, nr_to_pop should be updated to reflect that the new chunk could be created already populated. Otherwise an infinite loop might appear. Signed-off-by: Roman Gushchin --- mm/percpu.c | 63 +++++++++++++++++++++++++++++++++-------------------- 1 file changed, 39 insertions(+), 24 deletions(-) diff --git a/mm/percpu.c b/mm/percpu.c index 61339b3d9337..e20119668c42 100644 --- a/mm/percpu.c +++ b/mm/percpu.c @@ -1979,7 +1979,7 @@ static void pcpu_balance_free(enum pcpu_chunk_type = type) } =20 /** - * pcpu_balance_populated - manage the amount of populated pages + * pcpu_grow_populated - populate chunk(s) to satisfy atomic allocations * @type: chunk type * * Maintain a certain amount of populated pages to satisfy atomic alloca= tions. @@ -1988,35 +1988,15 @@ static void pcpu_balance_free(enum pcpu_chunk_typ= e type) * allocation causes the failure as it is possible that requests can be * serviced from already backed regions. */ -static void pcpu_balance_populated(enum pcpu_chunk_type type) +static void pcpu_grow_populated(enum pcpu_chunk_type type, int nr_to_pop= ) { /* gfp flags passed to underlying allocators */ const gfp_t gfp =3D GFP_KERNEL | __GFP_NORETRY | __GFP_NOWARN; struct list_head *pcpu_slot =3D pcpu_chunk_list(type); struct pcpu_chunk *chunk; - int slot, nr_to_pop, ret; + int slot, ret; =20 - /* - * Ensure there are certain number of free populated pages for - * atomic allocs. Fill up from the most packed so that atomic - * allocs don't increase fragmentation. If atomic allocation - * failed previously, always populate the maximum amount. This - * should prevent atomic allocs larger than PAGE_SIZE from keeping - * failing indefinitely; however, large atomic allocs are not - * something we support properly and can be highly unreliable and - * inefficient. - */ retry_pop: - if (pcpu_atomic_alloc_failed) { - nr_to_pop =3D PCPU_EMPTY_POP_PAGES_HIGH; - /* best effort anyway, don't worry about synchronization */ - pcpu_atomic_alloc_failed =3D false; - } else { - nr_to_pop =3D clamp(PCPU_EMPTY_POP_PAGES_HIGH - - pcpu_nr_empty_pop_pages[type], - 0, PCPU_EMPTY_POP_PAGES_HIGH); - } - for (slot =3D pcpu_size_to_slot(PAGE_SIZE); slot < pcpu_nr_slots; slot+= +) { unsigned int nr_unpop =3D 0, rs, re; =20 @@ -2060,12 +2040,47 @@ static void pcpu_balance_populated(enum pcpu_chun= k_type type) if (chunk) { spin_lock_irq(&pcpu_lock); pcpu_chunk_relocate(chunk, -1); + nr_to_pop =3D max_t(int, 0, nr_to_pop - chunk->nr_populated); spin_unlock_irq(&pcpu_lock); - goto retry_pop; + if (nr_to_pop) + goto retry_pop; } } } =20 +/** + * pcpu_balance_populated - manage the amount of populated pages + * @type: chunk type + * + * Populate or depopulate chunks to maintain a certain amount + * of free pages to satisfy atomic allocations, but not waste + * large amounts of memory. + */ +static void pcpu_balance_populated(enum pcpu_chunk_type type) +{ + int nr_to_pop; + + /* + * Ensure there are certain number of free populated pages for + * atomic allocs. Fill up from the most packed so that atomic + * allocs don't increase fragmentation. If atomic allocation + * failed previously, always populate the maximum amount. This + * should prevent atomic allocs larger than PAGE_SIZE from keeping + * failing indefinitely; however, large atomic allocs are not + * something we support properly and can be highly unreliable and + * inefficient. + */ + if (pcpu_atomic_alloc_failed) { + nr_to_pop =3D PCPU_EMPTY_POP_PAGES_HIGH; + /* best effort anyway, don't worry about synchronization */ + pcpu_atomic_alloc_failed =3D false; + pcpu_grow_populated(type, nr_to_pop); + } else if (pcpu_nr_empty_pop_pages[type] < PCPU_EMPTY_POP_PAGES_HIGH) { + nr_to_pop =3D PCPU_EMPTY_POP_PAGES_HIGH - pcpu_nr_empty_pop_pages[type= ]; + pcpu_grow_populated(type, nr_to_pop); + } +} + /** * pcpu_balance_workfn - manage the amount of free chunks and populated = pages * @work: unused --=20 2.30.2